Wheat is one of the three most important crops in the world, together with maize and rice. Approximately 600 million tonnes are harvested annually with cultivation extending over a vast geographical area, from Scandinavia to Argentina, including higher elevations in the tropics. Although the ability to give high yields under a range of conditions has contributed to the success of wheat, the most important factor has been the unique properties of wheat dough which allow it to be processed into a range of foodstuffs, notably bread, other baked products, and pastas. These properties are usually described as viscoelasticity, with the balance between the extensibility and elasticity determining the end use quality. For example, highly elastic (‘strong’) doughs are required for breadmaking, but more extensible doughs for making cakes and biscuits. The viscoelastic properties of dough are determined by the grain proteins, and in particular by the storage proteins which form a network in the dough called gluten (Schofield, 1994). Consequently, the gluten proteins have been widely studied over a period exceeding 250 years to determine their structures and properties and to provide a basis for manipulating and improving end use quality (Shewry et al., 1995).